1. Field of the Invention
The present invention relates to an image forming apparatus that uses an electrophotographic recording process, such as a laser printer, a copier, or a facsimile machine.
2. Description of the Related Art
Conventionally, toner discharge is known as a technology for electrophotographic image forming apparatuses. The toner discharge is, for example, an operation for forcedly discharging toner from a developing device on a regular basis and supplying the discharged toner to a cleaning blade for a photosensitive drum. The toner discharge needs to be executed from a developing roller for the following reason. That is, in a case of printing a large number of images having a low printing ratio, toner supplied from a toner container to a developing roller position remains within the developing device without being transferred, and degraded toner accumulates on a developing roller part. If the image forming (printing) is not performed for a certain period while the accumulated toner is left on the developing roller part, an adhesive force of toner may rise to cause toner fusion with respect to the developing roller and generate a defect image with lines caused by fixed toner in a toner-fused part. Therefore, an image forming apparatus needs a processing for forcedly discharging and removing toner on a regular basis in order to remove the toner remaining on the developing roller. In other words, it is necessary to discharge toner corresponding to one round of the developing roller.
Further, in a case where printing continues at a low printing ratio, a case where printing continues with small-size paper, a case where printing continues at high temperature and humidity, and other such cases, a cleaning blade for the photosensitive drum raises the following problems. That is, the cleaning blade may curl up, an edge portion of the cleaning blade may chip, or the cleaning blade may chatter (cause stick-slip). If curling up, the cleaning blade becomes unable to clean, and if the edge portion chips or chatters, toner runs through. As a measure against this phenomenon, Japanese Patent Application Laid-Open No. H09-034243 discloses a technology in which toner for discharge is distributed and supplied to each of cleaning blades and used as a lubricant to thereby prevent the cleaning blade from curling up and the edge portion from chipping or chattering.
As described above, the toner discharge has an object to clean out the degraded toner and perform maintenance of the cleaning blade. However, from the viewpoint of effective use of a toner resource, the toner consumed in the toner discharge does not play an original role of being formed as an image. Therefore, there is a demand that the toner consumed in the toner discharge be effectively used as an image.